Problems with AppleTV 4K Audio Sync

I've been having intermittent problems with audio sync on my AppleTV 4K. Sometimes its with streaming services (HBO Max or Amazon Plus), sometimes with home videos that I'm streaming from my own collection. I have calibrated my audio multiple times with my iPhone -- that's not the problem, because a video streaming from Netflix will play with perfectly synchronized audio at the same time a video from Amazon Prime will not. A home video that plays out of sync via AppleTV will play fine through VLC and Airplay on my TV (though if I airplay it through the Apple TV the sync problem remains). I'm assuming this is some sort of Dolby Vision/Atmos problem (I have my AppleTV set to play Dolby Vision 4K, and match dynamic range and frame rate). Any idea what might be causing these problems? What makes them especially frustrating is that they are intermittent and seem to be content-based (i.e. sometimes movies on HBO max play fine, and other times they are out of sync).